Commits are snapshots with tracking that enables diffing and histories. git very specifically focuses on commits containing complete information (snapshots) instead of older diffing models that would need to sometimes replay diffs to arrive at a commit state.
Mercurial took an interesting approach here. It stores commits as diffs with occasional snapshots in between. This is similar to how video codecs store frames as deltas with occasional full ‘keyframes’ in between. This is the way Mercurial blunts the diff-replay problem you mentioned.
Git AFAIK, stores each file modification as full snapshot, until it is packed at some stage. Mercurial doesn’t need this work around. Mercurial diffs are also format-neutral. It works fine with binary data.
Trust me, it’s a diff. I’ve seen a repo get into a very stupid state where there were changes in the main branch that weren’t in the develop branch, but a PR didn’t pick up those charges because they were somehow not in any of the commits
Depends on context.
Most of the interfacing is change based. But calling that diff is misleading.
